Many miniature electronic and optical devices are formed using layers of different materials stacked on each other. Examples of such devices include optical displays in which each pixel is formed in a patterned array, optical waveguide structures for telecommunication devices, and metal-insulator-metal stacks for semiconductor-based devices. A conventional method for making these devices includes forming one or more layers on a receptor substrate and patterning the layers simultaneously or sequentially to form the device. Patterning of the layers is often performed by photolithographic techniques that include, for example, covering a layer with a photoresist, patterning the photoresist by exposure to radiation through a mask, removing a portion of either the exposed or non-exposed photoresist to reveal the underlying layer according to the pattern, and then etching the exposed layer.
In many cases, multiple deposition and patterning steps are required to prepare the ultimate device structure. For example, the preparation of optical displays may require the separate formation of red, green, and blue pixels. Although layers may be commonly deposited for each of these types of pixels, some layers must be separately formed and often separately patterned. In some applications, it may be difficult or impractical to produce devices using conventional photolithographic patterning. There is thus a need for new methods of forming these devices. In at least some instances, this may allow for the construction of devices with more reliability and more complexity.
LITI has been developed as an alternative patterning method for multilayer microelectronic and optical devices. LITI is a digital patterning method involving the transfer of materials from a donor sheet to a receptor surface. LITI methods generally include pattern-wise printing of one or more transfer layers for display applications. LITI patterning methods typically use a multi-layer thermal transfer donor film that is pattern-wise exposed by a source of radiation (e.g., an infrared laser or flashlamp exposing through a mask) to transfer a patterned transfer layer from the donor film to a desired substrate.